1. Field of the Invention
The present invention relates to an aperture mechanism, and more particularly, to the aperture mechanism of the lens barrel for use in a monitoring camera or the like.
2. Description of the Related Art
The aperture mechanism of the lens barrel for use in a monitoring camera or the like usually has a holding frame for holding aperture blades and holding the aperture mechanism in the lens barrel, and a drive mechanism for opening and closing the aperture blades is fitted to this holding frame to unitize the aperture device.
Two types of drive mechanisms for opening and closing aperture blades are known, including for instance an electrical (automatic) type using an iris meter and a manual type for manual operation (see Japanese Patent Application Publication Nos. 9-281546 and 11-231190, etc.).
However, according to the prior art, an automatic aperture mechanism with an electrical drive mechanism and a manual aperture mechanism with a manual drive mechanism differ from each other in the shapes of the aperture blades and holding frame and the holding shape of the lens barrel among other aspects, and the production of the two types of aperture mechanisms as needed by users would entail an extra manufacturing cost.
Attempted in view of these circumstances, an object of the present invention is to provide an aperture mechanism permitting a substantial saving in manufacturing cost.
In order to achieve the object stated above, the present invention is directed to an aperture mechanism, comprising: aperture blades; a holding frame which holds the aperture blades; and a drive mechanism which opens and closes the aperture blades, the drive mechanism being fitted to the holding frame, wherein the holding frame is adapted to receive a desired one of an electrical drive mechanism which opens and closes the aperture blades electrically and a manual drive mechanism which opens and closes the aperture blades manually as the drive mechanism.
According to the present invention, since either an electrical drive mechanism or a manual drive mechanism can be fitted to a common holding frame, there is no need to alter the configuration of other constituent members than the drive mechanism, such as the shapes of the aperture blades and the holding frame or the holding form of the lens barrel according to whether the electrical drive mechanism or the manual drive mechanism is used, and therefore the manufacturing cost can be substantially reduced.
Preferably, the one of the electrical drive mechanism and the manual drive mechanism are capable of being attached to and detached from the holding frame as desired. Thus, the replacement of the electrical with the manual aperture mechanism, or vice versa, can be easily accomplished by making the electrical drive mechanism or the manual drive mechanism readily attachable to or detachable from the holding frame.
Preferably, a holding portion which holds the drive mechanism is formed on the holding frame; pin engaging portions which engage with drive pins of the drive mechanism and open and close the aperture blades by shifting of the drive pins are arranged on a face other than a holding face of the holding portion where the drive mechanism is held; a first hole through which a drive shaft of an iris meter for driving the drive pins in the electrical drive mechanism are inserted are provided in the holding face; and a second hole through which the drive pins in the manual drive mechanism are inserted are provided in the holding face. By thus making the holding frame, the electrical drive mechanism and the manual drive mechanism can be attachable to the common holding frame.
Preferably, the holding frame is capable of simultaneously receiving both the electrical drive mechanism and the manual drive mechanism, and the aperture blades are opened and closed with a desired one of the electrical drive mechanism and the manual drive mechanism. Instead of fitting only either an electrical drive mechanism or a manual drive mechanism to the holding frame, both drive mechanisms can be fitted at the same time, enabling the operator to accomplish iris adjustment with a desired one of the two drive mechanisms.